The disclosure relates to an optical receiver lens having a three-dimensional lens surface, and to an optical distance measuring device, in particular a laser distance measuring device.
Various types of optical distance measuring devices are described in US 2007/0030474 A1, WO 03/002939 A1, DE 10 051 302 C5, WO 2005/064359 A1, EP 00 701 702 B, WO 2006/024566 A1, and DE 43 16 348 A1.
Difficulties in the design of receiver optics for distance measuring devices stem from the stipulation that the distance measuring devices be capable of use for precise measurement both in the near range and in the far range. Problems in the measurement of large distances arise from extraneous light influences that have a negative effect on the signal-to-noise ratio. In order to reduce the extraneous light influence, the size of the photodetector that is used is usually tuned as well as possible to the size of the light point reflected by distant objects. With near field measurements, there is, inter alia, the problem that a parallax angle between an emitted light beam and a received light beam has a comparably strong effect on the measurement result. The parallax angle is to be ascribed to the fact that the transmitting lens system is arranged next to the receiver lens system. A further, important problem in the design of distance measuring devices that are intended to be used both for the near range and for the far range consists in that the received optical power is proportional to the inverse distance squared in the case of large distances. This results in the necessity to design the receiving system for processing weak signals. The sharp increase in the received laser power in the case of short distances lead, however, at the same time to the fact that the receiving system must be designed to be comparably inefficient for short distances in order to prevent saturation of the electronic detection circuitry.